1. Field of the Invention
The present invention relates to a semiconductor package and a semiconductor device, in particular, a semiconductor package for manufacturing a semiconductor device connected to an external antenna and a semiconductor device using the semiconductor package.
2. Description of Related Art
A semiconductor chip with radio communication function is used for a mobile communication device and an RFID (Radio Frequency IDentification). The semiconductor chip exchanges data with another mobile communication device or a reader/writer using a radio signal with a frequency in a frequency band of, for example, 2.45 GHz. The semiconductor chip is connected to an antenna suited to a used radio frequency band and performs radio communication with the other mobile communication device via the antenna. The semiconductor chip is typically provided with an RF (Radio Frequency) input/output circuit electrically connected to the antenna and a data processing unit which executes processing a digital signal and the like. The semiconductor chip may also include an input/output circuit for a digital signal or an analog signal. Such semiconductor chip includes a plurality of pad electrodes connected to an output terminal of the RF input/output circuit and an input/output terminal of the input/output circuit.
To protect a circuit mounted on the semiconductor chip against destruction due to ESD (Electrostatic Discharge), an ESD protection circuit is generally formed on the semiconductor chip.
FIGS. 1A and 1B are circuit diagrams showing an ESD protection circuit 3. FIG. 1A is a circuit diagram showing an example of the ESD protection circuit 3. A signal applied to a pad electrode 31 is supplied to an input buffer 34. The ESD protection circuit 3 is formed of a resistor 32, a diode 33 and a diode 35. A surge voltage applied to the pad electrode 31 by ESD is discharged into a power supply wiring 27 and a GND (GRounD) wiring 36 through the resistor 32 by the diode 33 and the diode 35. The surge voltage applied to the pad electrode 31 drops by the resistor 32 and is clamped by the diodes 33 and 35. Thereby, the ESD protection circuit 3 prevents the surge voltage of the pad electrode 31 from being directly applied to an input end of the input buffer 34.
FIG. 1B is an equivalent circuit diagram of the ESD protection circuit 3 in an AC operation in FIG. 1A. PN junctions included in the diode 33 and the diode 35 operate as a capacitor 331 and a capacitor 351, respectively, in the AC operation. As a result, the ESD protection circuit 3 serves as a low-pass filter formed of the resistor 32 and the capacitors 331, 351. Consequently, when the pad electrode 31 is connected to an antenna, characteristics of an AC signal, which is supplied from the antenna and has a frequency in the radio frequency band, are greatly degraded by the ESD protection circuit 3.
However, when the ESD protection circuit 3 is not connected to the pad electrode 31 connected to the antenna, ESD destruction becomes problem in handling of the semiconductor chip and the semiconductor device. This is the case where the RF input/output circuit which is not connected to the ESD protection circuit 3 via the pad electrode is electrically connected to an external terminal of the semiconductor device. In implementing such semiconductor device to the mobile communication device, when the surge voltage due to ESD is applied to the external terminal vulnerable to ESD destruction, the RF input/output circuit is destructed and the mobile communication device becomes a defective product. When the semiconductor device is implemented to the mobile communication device without application of the surge voltage due to ESD, the semiconductor chip is hard to cause ESD destruction in subsequent handling.
U.S. Pat. No. 7,095,372 B discloses an invention related to an integrated circuit package which has an antenna therein.
In this integrated circuit package, a semiconductor chip and a multiply-folded conductive pattern which serves as the antenna are mounted on a substrate. One end of the antenna is connected to the semiconductor chip with a bonding wire and the other end of the antenna terminates within the integrated circuit package without being connected to the external terminal of the integrated circuit package. That is, the conductive pattern which serves as the antenna is not connected to the external terminal, resulting in that the semiconductor chip connected to the conductive pattern with the bonding wire is not connected to the external terminal.
We have now discovered the following facts.
It is necessary to design the semiconductor device to be large in size when the antenna is installed therein. Surely, it is possible to fold the antenna complicatedly by exercise ingenuity based on the technique of loading coils.
However, when the antenna shortening technique is used, characteristics of the antenna are degraded, for example, a frequency band is narrowed and gain is lowered. Generally, an improvement of a distance capable of communication is the most important problem in general performances, and thus, a loss occurrence in the antenna is a grave defect.